overviewer/Minecraft-Overviewer — pull request #691 by CounterPillow (2012-04-10 23:14:13+00:00)
Title: Save png images with an adaptive palette

Reduces file size significantly without any noticeable loss in quality. (If even any at all.)
This is extremely hacky, someone should go over this *!*oneliner*!*. Apparently PIL can't convert directly from RGBA to P, so it uses RGB first. Weird.